KR20120109320A - Heavy duty pneumatic tire - Google Patents

Abstract

PURPOSE: A pneumatic tire for heavy weight is provided to secure the high performance of a center wear resistance function and a hill and tow wear resistance. CONSTITUTION: A pneumatic tire(1) for heavy weight comprises a tread portion(2). A center main groove(3A), a middle main groove(3B), and a shoulder main groove(3C). The tread portion is divided into a center land portion(4A), a middle land portion(4B), and a shoulder land portion(4C). The center main groove and the middle main groove are extended along the circumferential direction of a tire. The shoulder main groove is formed in the both external sides of the middle main groove. A center tie bar(16A), a middle tie bar(16B), and a shoulder tie bar(16C) are formed in a center cross groove(7A), a middle cross groove(7B) and a shoulder cross groove(7C) respectively.

Description

Heavy-duty pneumatic tires {HEAVY DUTY PNEUMATIC TIRE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty pneumatic tire capable of achieving both high center wear resistance and high heel & toe wear resistance.

Heavy-pneumatic pneumatic tires used in trucks, buses, and the like are not easy to replace tires, so they must be able to run all season and high traction performance is required. For this reason, the block pattern which divided | segmented several blocks into the tread part of such a heavy load pneumatic tire is employ | adopted widely.

However, such a heavy-load pneumatic tire has a problem that so-called center wear, which causes a relatively large wear of the center block, is likely to occur. In order to prevent such center wear, the following patent document 1 is proposed.

Patent Document 1: Japanese Patent Application Laid-Open No. 2007-22151

In the heavy-load pneumatic tire of Patent Literature 1, a configuration in which the groove inclination angle of the center lateral groove is made larger than the shoulder lateral groove is adopted, whereby the block stiffness of the center block is relatively increased, and the center wear resistance is improved.

However, in the heavy-load pneumatic tire of Patent Literature 1, the block rigidity of the shoulder block is relatively small, and there is a problem that heel & toe wear, which is prematurely worn at the end of the first side and the rear side of the block, tends to occur. there was.

The present invention has been devised in view of the above-described situation, and forms a center tie bar, a middle tie bar and a shoulder tie bar in which the bottom of the groove is raised in the center cross groove, the middle cross groove and the shoulder cross groove, respectively, and the shoulder tie Based on the maximum height of the ridge height of the bar and defining the maximum width Wcr of the center land portion, the maximum width Wmi of the middle land portion and the maximum width Wsh of the shoulder land portion within a certain range, The main object of the present invention is to provide a heavy-duty pneumatic tire capable of achieving both high performance and high heel & toe wear resistance.

The invention according to claim 1 of the present invention includes a center main groove extending continuously on the tire equator in the tire circumferential direction and a pair of middle main grooves extending continuously in both sides of the center main groove in the tire circumferential direction. And a pair of shoulder main grooves extending continuously from both outer sides of the middle main groove in the tire circumferential direction, such that a center land portion between the center main groove and the middle main groove, the middle main groove and the shoulder are formed in the tread portion. A middle land portion between the main groove, and a shoulder land portion between the shoulder main groove and the tread ground end are divided, and the center land portion, the middle land portion, and the shoulder land portion are each a center cross groove, a middle cross groove, and a shoulder cross groove, respectively. A heavy-load pneumatic tire divided into a center block, a middle block and a shoulder block, wherein the center lateral groove, middle lateral groove and shoulder In the horizontal groove, a center tie bar, a middle tie bar and a shoulder tie bar, each of which has raised the bottom of the groove, are formed, and the raised height of the shoulder tie bar is the largest, and the maximum width of the center land part is Wcr and the maximum width of the middle land part. When Wmi and the maximum width of the shoulder land portion is Wsh, the following relationship is satisfied.

0.9≤Wmi / Wcr≤0.98

1.1≤Wsh / Wcr≤1.22

Moreover, invention of Claim 2 is a heavy-load pneumatic tire of Claim 1 whose ratio (Wsh / Wmi) is 1.12-1.36.

In addition, in the invention according to claim 3, an intermediate point in the tire axial direction of the center tie bar and the middle tie bar is located in a center region of the tire axial direction of the center cross groove and the middle cross groove, The intermediate point of the tire axial direction is a heavy-load pneumatic tire according to claim 1 or 2 located in an outer region of the tire axial direction of the shoulder lateral groove.

The invention according to claim 4 is the heavy-load pneumatic tire according to any one of claims 1 to 3, wherein the maximum raised height of the shoulder tie bar is 70 to 85% of the maximum groove depth of the shoulder main groove.

In addition, according to the invention of claim 5, the center block, the middle block and the shoulder block are each of any of claims 1 to 4 in which a siping extending in the tire axial direction is formed in a central region of the tire circumferential direction of the block. The heavy duty pneumatic tire according to claim 1.

The invention according to claim 6 is the heavy-load pneumatic tire according to claim 5, wherein a difference between the maximum groove depth of the shoulder tie bar and the maximum depth of the sipping of the shoulder block is 30% or more of the maximum groove depth of the shoulder main groove. to be.

In addition, in this specification, unless otherwise specifically understood, the dimension of each part of a tire shall be a value specified in the normal state of the no load which rim-assembled to the normal rim and the normal internal pressure was filled.

The "regular rim" is a rim that is defined for each tire in a standard system including a standard on which the tire is based, for example, a standard rim for JATMA, "Design Rim" for TRA, or "Measuring Rim" for ETRTO. Means.

The above-mentioned "regular internal pressure" is the air pressure prescribed | regulated by the said tire for every tire, the maximum air pressure in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

The heavy-load pneumatic tire of the present invention includes a center main groove extending continuously over the tire equator in the tire circumferential direction, a pair of middle main grooves extending continuously in both sides of the center main groove in the tire circumferential direction, A pair of shoulder main grooves are formed which extend both outer sides of the middle main groove in the tire circumferential direction. Accordingly, the tread portion is divided into a center land portion between the center main groove and the middle main groove, a middle land portion between the middle main groove and the shoulder main groove, and a shoulder land portion between the shoulder main groove and the tread ground end.

In addition, the center land portion, the middle land portion, and the shoulder land portion are divided into a center block, a middle block, and a shoulder block by a center cross groove, a middle cross groove, and a shoulder cross groove, respectively. This block pattern helps to exhibit high traction performance.

In addition, center tie grooves, middle tie grooves, and shoulder cross grooves are formed with center tie bars, middle tie bars, and shoulder tie bars with raised groove bottoms, respectively. Such a tie bar can reduce the stiffness difference in the tire circumferential position at each land portion, and can improve heel & toe wear resistance. Moreover, since the ridge height of the shoulder tie bar is set to be the largest among each tie bar, it is possible to effectively prevent the wear of the heel & toe and the missing portion that tend to occur in the shoulder land portion.

Further, when the maximum width of the center land portion is Wcr, the maximum width of the middle land portion is Wmi, and the maximum width of the shoulder land portion is Wsh, the following relationship is satisfied.

0.9≤Wmi / Wcr≤0.98

1.1≤Wsh / Wcr≤1.22

As a result, the block stiffness of the center block having a relatively large ground pressure is relatively high, so that the center wear resistance can be improved. Moreover, since the block rigidity of the shoulder block is also sufficiently secured, heel & toe wear or partial missing wear can be effectively prevented. Therefore, the heavy-load pneumatic tire of this invention can make both center wear resistance and heel & toe wear performance high in both dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS The tread development figure which shows the heavy duty pneumatic tire of this embodiment.
2 is a sectional view taken along the line AA in Fig.
3 is an enlarged view of a center land portion.
4 is an enlarged view of the middle land portion.
5 is an enlarged view of a shoulder land portion.
6 is a cross-sectional view taken along line BB of FIG. 1.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the heavy-load pneumatic tire (henceforth simply a "tire") of this embodiment is used for heavy-load vehicles, such as a truck and bus.

The tread portion 2 of the tire 1 of the present embodiment includes a center main groove 3A extending on the tire equator C in the tire circumferential direction and a pair of pairs extending from both outer sides of the center main groove 3A. The middle main groove 3B and a pair of shoulder main grooves 3C extending from both outer sides of the middle main groove 3B are formed. Accordingly, the tread portion 2 includes a pair of center land portions 4A between the center main grooves 3A and the middle main grooves 3B, and a middle land portion between the middle main grooves 3B and the shoulder main grooves 3C. 4B) and the shoulder land portion 4C between the shoulder main groove 3C and the tread ground end 2t.

In the present specification, the "tread ground end 2t" is set as the edge when it can be identified by an apparently apparent edge. However, when the identification is impossible, a normal load is applied to the tire 1 in the normal state. When the tread part 2 is grounded to the plane at the camber angle of 0 degrees, the ground end that is grounded to the plane at the outermost tire axial direction is determined as the tread ground end 2t.

The above-mentioned "normal load" is a load defined for each tire in the standard system including the standard on which the tire is based, the maximum load capacity for JATMA, and the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. In the case of the maximum value described in ETRTO, "LOAD CAPACITY" is assumed.

The center main groove 3A, the middle main groove 3B, and the shoulder main groove 3C of the present embodiment extend continuously in the tire circumferential direction while bending in a zigzag shape. These main grooves 3A, 3B and 3C can exert an edge component in the tire circumferential direction, which helps to increase traction performance. Preferably, the groove widths W1a, W1b, and W1c of the main grooves 3A, 3B, and 3C are about 6 to 9 mm, and the maximum groove depths D1a, D1b, and D1c (shown in Fig. 2) are 14 to 22. mm is preferred.

As shown in an enlarged view in FIG. 3, the center main groove 3A has a steep inclination portion 5A inclined at an angle α1a of about 5 to 15 degrees with respect to the tire circumferential direction, and 30 to 30 with respect to the tire circumferential direction. It consists of 6A of inclination parts inclined by the angle (alpha) 1b about 50 degree | times, These steep inclination part 5A and 6A of inclination parts are alternately arrange | positioned in a tire circumferential direction.

The center main groove 3A can smoothly guide the water film interposed between the outer surface 2S and the road surface of the tread portion 2 by the steep inclination portion 5A having a small angle α1a in the tire circumferential direction. Thereby, the drainage performance can be improved. Further, the center main groove 3A can improve the traction performance because the lightly inclined portion 6A having a large angle α1b can effectively exhibit the edge component in the tire axial direction.

Moreover, it is preferable that 5 A of steep inclination parts are set to the length L1a of the tire circumferential direction larger than the length L1b of the tire circumferential direction of 6A of mild inclination parts. As a result, the steep slope 5A can guide the water film more smoothly, and can further improve drainage performance. Preferably, the length L1a of the steep inclined portion 5A is preferably about 5 to 10 times the length L1b of the light inclined portion 6A.

As shown in an enlarged view in FIG. 4, the middle main groove 3B includes a first inclined portion 5B inclined to one side with respect to the tire circumferential direction, and a second inclined portion inclined to the other side with respect to the tire circumferential direction ( 6B), and these first and second inclined portions 5B, 6B are alternately arranged in the tire circumferential direction.

In addition, each angle (alpha) 2a, (alpha) 2b with respect to a tire circumferential direction, and each length L2a, L2b of a tire circumferential direction are set the same in the 1st inclination part 5B and the 2nd inclination part 6B. Thereby, the middle main groove 3B can raise the traction performance and drainage performance by an edge component in a balanced manner. Preferably, the angles α2a and α2b are about 5 to 15 degrees, and the lengths L2a and L2b in the tire circumferential direction are preferably about 40 to 60% of the lengths L1a + L1b / 2.

The shoulder main groove 3C includes a first inclined portion 5C and a second inclined portion 6C, similarly to the middle main groove 3B, as shown in an enlarged view in FIG. 5. 2 inclination parts 5C and 6C are alternately arrange | positioned in a tire circumferential direction. The first and second inclined portions 5C and 6C have the same angles α3a and α3b with respect to the tire circumferential direction and respective lengths L3a and L3b in the tire circumferential direction, and the zigzag phase Since it is arrange | positioned at the half pitch from this middle main groove 3B, traction performance and drainage performance can be improved in a balanced manner. Preferably, the angles α3a and α3b are also about 5 to 15 degrees, and the lengths L3a and L3b in the tire circumferential direction are preferably about 40 to 60% of the lengths L1a + L1b / 2.

As shown in Fig. 1, the center land portion 4A is formed with a center lateral groove 7A extending between the center main groove 3A and the middle main groove 3B and spaced apart in the tire circumferential direction. . As a result, the center land portion 4A is formed with the center block 8A separated by the center lateral groove 7A spaced apart in the tire circumferential direction.

As shown in FIG. 3, the center lateral groove 7A communicates the steep inclination portion 5A of the center main groove 3A and the zigzag peak 3Bi that is convex in the tire axial direction of the middle main groove 3B. And inclined at an angle α7a of about 5 to 15 degrees.

The center lateral groove 7A can exhibit an edge component in the tire circumferential direction and the tire axial direction, and can improve traction performance and steering stability. In addition, the center lateral groove 7A can smoothly guide the water film interposed between the outer surface 2S (shown in FIG. 2) and the road surface of the tread portion 2 along the inclination thereof, and drainage performance. Can improve. In order to exert such an effect effectively, the groove width W7a (shown in FIG. 1) of the center lateral groove 7A is about 14 to 17 mm, and the maximum groove depth D7a (shown in FIG. 2) is 15 to 25 mm is preferred.

In the center block 8A, the block edge 8As facing the center main groove 3A of the center block 8A is zigzag by a pair of steep slopes 5A and 5A and a soft slope portion 6A. Brother In the center block 8A, the block edge 8At facing the middle main groove 3B is formed by the first inclined portion 5B and the second inclined portion 6B of the middle main groove 3B. A horizontal V-shape is formed to be convex outward in the axial direction.

As a result, the center block 8A has a tread surface that increases in width in the tire axial direction W4a toward the center from the block edge 8Aa on one end side in the tire circumferential direction, and on the other end side in the tire circumferential direction. The width W4a is formed approximately equally from the block edge 8Ab toward the center. Such a center block 8A can effectively exhibit the edge components with respect to a tire circumferential direction and a tire axial direction, and can improve traction performance and steering stability performance.

In the center block 8A, the sipping S1 extending in the tire axial direction is formed in the center region T4a in the tire circumferential direction. Such siping S1 partially lowers the rigidity of the center block 8A, can alleviate the stiffness step in the tire circumferential direction of the center land portion 4A, and can effectively prevent center wear.

Here, the "center area T4a of the center block 8A" has a length of 35% of the maximum length L4a of the tire circumferential direction of the center block 8A, and centers the center of the tire circumferential direction in the center block ( Let it be an area | region coinciding with the center of the tire circumferential direction of 8A), and let the tire circumferential direction outer side of this center area | region T4a be "outer area."

The siping S1 includes a pair of main parts 13A and 13A extending inwardly from each other from block edges 8As and 8At on both outer sides of the tire axial direction, and the main parts 13A and 13A. It includes a sub portion 14A extending inclined with respect to the tire circumferential direction between the inner end in the tire axial direction of the (), and is formed in a substantially inverted Z shape.

Such siping S1 can increase the edge length and reduce the block stiffness as compared with the linear one, and thus can effectively prevent center wear while maintaining traction performance. Preferably, the maximum depth (not shown) of the siping S1 is preferably about 1 to 4 mm.

As shown in FIG. 1, the middle land portion 4B is formed with a middle lateral groove 7B which communicates with the middle main groove 3B and the shoulder main groove 3C and is spaced apart in the tire circumferential direction. Accordingly, the middle block 4B is formed in the middle land portion 4B so as to be spaced apart in the tire circumferential direction.

As shown in FIG. 4, the middle lateral groove 7B is convex in the tire axial direction of the zigzag peak 3Bo and the shoulder main groove 3C which are convex in the tire axial direction outer side of the middle main groove 3B. Communication is performed between zigzag vertices 3Ci. In addition, as shown in FIG. 1, the middle lateral groove 7B is arranged to be shifted approximately half pitch from the center lateral groove 7A adjacent to the tire axial direction in the tire circumferential direction, and the center lateral groove 7A and the center lateral groove 7A. It is inclined in the opposite direction and extends.

This middle lateral groove 7B, like the center lateral groove 7A, also helps to improve traction performance, steering stability performance and drainage performance. Preferably, the groove width W7b (shown in FIG. 1) of the middle lateral groove 7B is about 5-20 mm, the maximum groove depth D7b (shown in FIG. 2) is about 18-22 mm, As for the angle (alpha) 7b (shown in FIG. 4) with respect to a tire axial direction, 5-15 degrees are preferable.

In the middle block 8B, a block edge 8Bs facing the middle main groove 3B is formed by a first shaft 5B and a second inclined portion 6B of the middle main groove 3B. It is formed in the horizontal V shape which becomes convex in a direction inside. On the other hand, the block edge 8Bt facing the shoulder main groove 3C is convex outwardly in the tire axial direction by the first inclined portion 5C and the second inclined portion 6C of the shoulder main groove 3C. It forms a horizontal V shape. Thereby, the width | variety W4b of a tire axial direction increases in the tread surface of the middle block 8B toward the center, respectively in the block edge 8Ba, 8Bb of the tire circumferential direction both sides.

Such middle block 8B can also effectively exhibit the edge components in the tire circumferential direction and the tire axial direction, and can improve traction performance and steering stability.

Further, in the middle block 8B, vertically elongated recesses 18 which reduce the rubber volume are formed in the convex portions 17s that are convex in the tire axial direction inside of the block edge 8Bs. Such concave portions 18 can alleviate the block stiffness in the tire axial direction in which the ground pressure is relatively increased on the tread surface of the middle block 8B, and can effectively prevent heel & toe wear.

Moreover, the sipping S2 extended in a tire axial direction is formed in the middle block 8B in the center area | region T4b of the tire circumferential direction. Similar to the siping S1 formed in the center block 8A, this siping S2 is also formed in substantially Z shape including a pair of main part 13B, 13B and the sub part 14B. . Such siping S2 can also effectively prevent heel & toe wear while maintaining traction performance. Preferably, the maximum depth (not shown) of the siping S2 is preferably about 1 to 4 mm.

Here, the "center area T4b of the middle block 8B" has a length of 35% of the maximum length L4b in the tire circumferential direction of the middle block 8B, and the center of the tire circumferential direction is the middle block ( It is set as the area | region coinciding with the center of the tire circumferential direction of 8B), and let the tire circumferential direction outer side of the said center area | region T4b be "outer area."

As shown in Fig. 1, the shoulder land portion 4C is formed with a shoulder lateral groove 7C which communicates with the shoulder main groove 3C and the tread ground end 2t and is spaced apart in the tire circumferential direction. . As a result, the shoulder block 8C is formed in the shoulder land portion 4C so as to be spaced apart from the tire circumferential direction by the shoulder block 8C separated by the shoulder lateral groove 7C.

As shown in FIG. 5, the shoulder lateral groove 7C communicates between the zigzag peak 3Co and the tread ground end 2t, which are convex from the tire axial direction outside of the shoulder main groove 3C, and the middle lateral. It is inclined and extended in the same direction as the groove 7B. In addition, as shown in FIG. 1, the shoulder lateral groove 7C is disposed to be approximately half pitch shifted from the middle lateral groove 7B adjacent in the tire axial direction.

This shoulder lateral groove 7C also helps to improve traction performance, steering stability performance and drainage performance. In addition, as shown in FIG. 2, since the maximum groove depth D7c of the shoulder lateral groove 7C is set smaller than the center lateral groove 7A and the middle lateral groove 7B, the heel & toe The stiffness step in the tire circumferential direction of the shoulder land portion 4C, which tends to cause wear relatively, can be effectively alleviated. Preferably, the groove width W7c (shown in FIG. 1) of the shoulder lateral groove 7C is about 5 to 20 mm, the maximum groove depth D7c is about 14 to 17 mm, and the angle with respect to the tire axial direction ( (alpha) 7c) (shown in FIG. 5) is preferably about 5 to 15 degrees.

As for the shoulder block 8C, as shown in FIG. 5, the block edge 8Cs which face 3C of shoulder main grooves are the 1st inclination part 5C and the 2nd inclination part of 3 C of shoulder main grooves. By 6C, the block edge 8Ct which forms the horizontal V shape which becomes convex in a tire axial direction inner side, and faces the tread ground end 2t is extended along a tire circumferential direction.

As a result, the tread surface of the shoulder block 8C increases in the tire axial direction width W4c toward the center from the block edges 8Ca and 8Cb on both sides in the tire circumferential direction, thereby increasing traction performance and steering stability. It can improve performance.

In the shoulder block 8C, the sipping S3 extending in the tire axial direction is formed in the center region T4c in the tire circumferential direction. The sipping S3 is also formed in a substantially inverted Z shape including the pair of main parts 13C and 13C and the sub part 14C, and can effectively prevent heel & toe wear while maintaining traction performance. have. Preferably, the maximum depth D2c (shown in FIG. 6) of the sipping S3 is preferably about 1 to 4 mm.

Here, the "center area T4c of the shoulder block 8C" has a length of 35% of the maximum length L4c in the tire circumferential direction of the shoulder block 8c, and the center thereof is the tire of the shoulder block 8C. Let it be an area | region coinciding with the center of a circumferential direction, and let the tire circumferential direction outer side of the said center area | region T4c be "outer area."

As shown in FIG. 1, in this embodiment, the center tie bar 16A and middle tie which raised the groove bottom in the center cross groove 7A, the middle cross groove 7B, and the shoulder cross groove 7C, respectively. Bar 16B and shoulder tie bar 16C are formed.

As shown in FIG. 3, the center tie bar 16A extends in the tire circumferential direction after the center blocks 8A and 8A adjacent in the tire circumferential direction.

The center tie bar 16A connects the center blocks 8A and 8A adjacent in the tire circumferential direction to increase the circumferential rigidity of the center land portion 4A (shown in FIG. 1), thereby providing traction. It helps to increase performance and effectively prevents center wear.

On the other hand, as shown in FIG. 2, although the maximum raised height H1 of the center tie bar 16A can be set suitably, when there is a small thing, there exists a possibility that the above-mentioned effect cannot be exhibited effectively. On the contrary, even if the maximum raised height H1 is too large, the groove volume of the center lateral groove 7A is excessively small, and there is a fear that the drainage performance is lowered. In this respect, the maximum raised height H1 is preferably at least 30%, more preferably at least 40%, and preferably at least 70% of the maximum groove depth D1b of the middle main groove 3B. Hereinafter, More preferably, it is 60% or less.

On the other hand, the raised height of the tie bar is determined by the difference between the maximum groove depth of the main groove and the maximum groove depth of the tie bar, based on the main groove having the largest maximum groove depth among the main grooves in which the tie bar is adjacent in the tire axial direction. . In the case of the center tie bar 16A, it is measured by the difference of the maximum groove depth D1b of the middle main groove 3B, and the maximum groove depth D3a of the center tie bar 16A.

Similarly, as shown in FIG. 3, the maximum length L6a in the tire axial direction of the center tie bar 16A is preferably 30 of the maximum length L7a in the tire axial direction of the center lateral groove 7A. % Or more, More preferably, it is 40% or more, Preferably it is 70% or less, More preferably, it is 60% or less.

In the center land portion 4A, center wear and heel & toe wear tend to occur at the center portion of the tire axial direction. For this reason, it is preferable that the intermediate point 16Ac of the tire axial direction of the center tie bar 16A is located in the center area | region T7a of the tire axial direction of the center lateral groove 7A. As a result, the center tie bar 16A can effectively alleviate the stiffness step in the tire circumferential direction at the center portion of the tire axial direction of the center land portion 4A, thereby preventing center wear.

Here, the "center area T7a of the center lateral groove 7A" has a length of 35% of the maximum length L7a in the tire axial direction of the center lateral groove 7A, and the center thereof is the center lateral groove 7A. ), And the tire axial direction outer side of the center area T7a is referred to as an "outer area".

As shown in FIG. 4, the middle tie bar 16B extends in the tire circumferential direction after the middle blocks 8B and 8B adjacent in the tire circumferential direction. This middle tie bar 16B also helps to improve traction performance while preventing heel & toe wear.

In addition, as shown in FIG. 2, the maximum raised height H2 of the middle tie bar 16B is preferably the same as the center tie bar 16A, and preferably the maximum groove depth of the middle main groove 3B. 30% or more of D1b), more preferably 40% or more, and preferably 70% or less, and more preferably 60% or less.

Similarly, as shown in FIG. 4, the maximum length L6b in the tire axial direction of the middle tie bar 16B is preferably 30 of the maximum length L7b in the tire axial direction of the middle lateral groove 7B. % Or more, More preferably, it is 40% or more, Preferably it is 70% or less, More preferably, it is 60% or less.

In addition, it is preferable that the intermediate point 16Bc of the tire axial direction of the middle tie bar 16B is located in the center area | region T7b of the tire axial direction of the middle lateral groove 7B. Thereby, the middle tie bar 16B can prevent heel & toe wear effectively like the center tie bar 16A.

Here, the "center region T7b of the middle lateral groove 7B" has a length of 35% of the maximum length L7b in the tire axial direction of the middle lateral groove 7B, and the center thereof is the middle lateral groove 7B. ), And the tire axial direction inner side of the center region T7b is referred to as the "inner region", and the tire axial direction outer side is referred to as the "outer region".

As shown in Fig. 5, the shoulder tie bar 16C is also formed to extend between the shoulder blocks 8C and 8C adjacent in the tire circumferential direction in the tire circumferential direction, preventing heel & toe wear, It helps to improve traction performance.

In addition, as shown in FIG. 2, the maximum raised height H3 of the shoulder tie bar 16C is set largest compared with the center tie bar 16A and the middle tie bar 16B. As a result, the shoulder tie bar 16C can effectively increase the rigidity of the shoulder land portion 4C, which is most likely to cause heel & toe wear and partial missing wear, among all land portions 4A, 4B, and 4C.

On the other hand, when the maximum raised height H3 of the shoulder tie bar 16C is small, there exists a possibility that the above-mentioned effect cannot be exhibited effectively. On the contrary, even if the maximum raised height H3 is too large, there is a fear that the drainage performance is lowered. In this respect, the maximum raised height H3 is preferably 70% or more, more preferably 75% or more, and preferably 85% or less, more preferably 70% or more of the maximum groove depth of the shoulder lateral groove 7C. Preferably it is 80% or less.

Similarly, as shown in FIG. 5, the maximum length L6c in the tire axial direction of the shoulder tie bar 16C is preferably 30 of the maximum length L7c in the tire axial direction of the shoulder lateral groove 7C. % Or more, More preferably, it is 40% or more, Preferably it is 70% or less, More preferably, it is 60% or less.

In the shoulder land portion 4C, since the heel & toe wear and the partial missing wear easily occur outside the tire axial direction, the middle point 16Cc in the tire axial direction of the shoulder tie bar 16C is the shoulder lateral groove. It is preferable to be located in the outer region T7c in the tire axial direction of 7C.

Here, the "outer region T7c of the shoulder lateral groove 7C" has a length of 40% of the maximum length L7c in the tire axial direction of the shoulder lateral groove 7C, and the tire axial outer end thereof is tread. Let it be an area | region coinciding with the ground end 2t, and let the tire axial direction inner side of the said outer area | region T7c be an "inner area".

6, the difference D3c-D2c between the maximum groove depth D3c of the shoulder tie bar 16C and the maximum depth D2c of the sipping S3 of the shoulder block 8C is determined. It is preferable that it is 30% or less of the maximum groove depth D1c of the shoulder main groove 3C. As a result, the rigid step formed by the shoulder block 8C and the shoulder lateral groove 7C can be more effectively reduced, and heel & toe wear can be effectively prevented.

On the other hand, when ratio ((D3c-D2c) / D1c) exceeds 30%, the above-mentioned effect cannot be exhibited. On the contrary, when the said ratio D3c-D2c / D1c is too small, the force which the shoulder blocks 8C mutually support mutually becomes small, and there exists a possibility that heel & toe wear may arise. From this point of view, the ratio ((D3c-D2c) / D1c) is preferably 20% or less, and more preferably 10% or more.

Moreover, as shown in FIG. 1, in this embodiment, the maximum width of the center land part 4A (center block 8A) is Wcr and the maximum width of the middle land part 4B (middle block 8B). When the maximum width of Wmi and the shoulder land portion 4C (shoulder block 8C) is Wsh, the following relationship is satisfied.

0.9≤Wmi / Wcr≤0.98

1.1≤Wsh / Wcr≤1.22

As a result, the block stiffness of the center block 8A having a relatively large ground pressure is relatively high, so that center wear can be effectively prevented. Moreover, since the block rigidity of the shoulder block 8C is also sufficiently secured, heel & toe wear and partial missing wear can be effectively prevented.

In addition, after securing the rigidity of the shoulder land portion 4C, the width of the land portion is relatively narrowed to reduce the difference in the ground pressure in the tire axial direction. In the present invention, since the shoulder tie bar 16C is largely set while the land portion width of the shoulder land portion 4C is relatively narrowed, the tie bar attaching region and the non-installation region in the shoulder land portion 4C. The difference in the amount of wear in the width direction can be reduced by reducing the stiffness difference generated in the widthwise direction, and the occurrence of uneven wear can be suppressed.

Therefore, the tire 1 of this embodiment can make both center wear resistance and heel & toe wear performance high in both dimensions.

When the ratio Wmi / Wcr exceeds 0.98, the block stiffness of the center block 8A is excessively small, and there is a possibility that the center wear cannot be sufficiently prevented. On the contrary, when the ratio Wmi / Wcr is less than 0.9, the block stiffness of the middle block 8B is excessively small, and there is a fear that heel & toe wear cannot be sufficiently prevented. From this point of view, the ratio (Wmi / Wcr) is preferably 0.98 or less, more preferably 0.96 or less, and preferably 0.9 or more, and more preferably 0.92 or more.

From the same point of view, (Wsh / Wcr) is preferably 1.22 or less, more preferably 1.18 or less, and preferably 1.10 or more, and more preferably 1.14 or more.

Further, when the median value 0.94 of the range of the ratio (Wmi / Wcr) and the median value (1.16) of the range of the ratio (Wsh / Wcr) are reference values of the ratio, the ratio (Wmi / Wcr) and the ratio (Wsh / It is preferable that all of Wcr) is below a reference value or more than a reference value. Thereby, the rigid balance of the middle block 8B and the shoulder block 8C can be maintained, and heel & toe wear can be suppressed effectively.

On the other hand, when the ratio Wmi / Wcr is larger than the reference value and the ratio Wsh / Wcr is smaller than the reference value, the stiffness difference between the middle block 8B and the shoulder block 8C becomes excessively small, and the shoulder block 8C There is a possibility that the heel & toe wear of) cannot be prevented enough. On the contrary, when the ratio Wmi / Wcr is smaller than the reference value and the ratio Wsh / Wcr is larger than the reference value, the stiffness difference between the middle block 8B and the shoulder block 8C becomes excessively large, so that the middle block 8B There is a fear that heel & toe wear cannot be prevented sufficiently.

As mentioned above, although especially preferable embodiment of this invention was described in detail, this invention is not limited to embodiment shown, It can variously deform and implement.

[Example]

The tire which has the basic structure shown in FIG. 1, and has a center land part, a middle land part, a shoulder land part, etc. which were shown in Table 1 was manufactured, and these performances were evaluated. On the other hand, common specifications are as follows.

Tire size: 11.00R20

Rim Size: 20 × 8.00

Center main home, middle main home, shoulder main home:

Groove width (W1a, W1b, W1c): 6 to 9 mm

Groove depth (D1a, D1b, D1c): 20.4 mm

Mild slope: Angle (α1a): 10 degrees

Length (L1a): 45 mm

Steep slope: Angle (α1b): 40 degrees

Length (L1b): 5 mm

1st, 2nd inclination part: angle ((alpha) 2a, alpha2b, alpha3a, alpha3b): 10 degree

Length (L2a, L2b, L3a, L3b): 22 mm

Center Groove, Middle Groove, Shoulder Groove:

Angle (α7a, α7 b, α7c): 10 degrees

Groove width (W7a, W7b, W7c): 5-20 mm

Groove depth (D7a, D7b, D7c): 15.4 to 20.4 mm

Maximum length (L7a, L7b, L7c): 20 to 50 mm

Center block:

Maximum Length (L4a): 40 mm

Center area (T4a): 14 mm

Ratio (T4a / L4a): 35%

Middle block:

Maximum length (L4b): 42 mm

Center area (T4b): 14.7 mm

Ratio (T4b / L4b): 35%

Shoulder block:

Maximum Length (L4c): 40 mm

Center area (T4c): 14 mm

Ratio (T4c / L4c): 35%

Center tie bar:

Groove depth (D3a): 10.2 mm

Maximum elevation height (H1): 10.2 mm

Maximum length (L6a): 16 mm

Center area (T7a): 11.2 mm

Ratio (H1 / D1a): 50%

Ratio (L6a / L7a): 50%

Ratio (T7a / L7a): 35%

Middle tie bar:

Groove depth (D3b): 10.2 mm

Maximum elevation height (H2): 10.2 mm

Maximum length (L6b): 16 mm

Center area (T7b): 11.2 mm

Ratio (H2 / D1b): 50%

Ratio (L6b / L7b): 50%

Ratio (T7b / L7b): 35%

Shoulder tie bar:

Maximum length (L6c): 20 mm

Outer area (T7c): 16 mm

Ratio (L6c / L7c): 50%

Ratio (T7c / L7c): 40%

Depth of siping (S1, S2): 2.5 mm

The test method is as follows.

Center wear resistance

Each rim tire was rim-assembled on the rim, filled with internal pressure of 780 kPa, and mounted on all wheels of an 8-ton 2-D car, driving 80,000 km on a general road / highway in a static state. After that, the ratio (center wear index) of the maximum wear amount of the center block and the maximum wear amount of the shoulder block was measured. In addition, the difference in the amount of wear between the first edge and the rear edge of the shoulder block and the ratio (heel & toe wear index) of the maximum groove depth of the shoulder main groove were measured in the same manner. In all cases, the smaller the value, the better.

<Heel and toe wear resistance of middle block and shoulder block>

After the rims are assembled on the vehicle under the above conditions, the vehicle is mounted, and after traveling 80,000 km on the general road / highway in a static state, the difference between the amount of wear on the first side edge and the rear side edge of the middle block and the middle main groove Ratio of the maximum groove depth of the middle block (heel & toe wear index of the middle block) and the difference in the amount of wear between the first edge and the trailing edge of the shoulder block and the ratio of the maximum groove depth of the shoulder main groove (heel & toe wear of the shoulder block) Index). In all cases, the smaller the value, the better.

<Drain performance>

Each test tire was rim-assembled under the above conditions, mounted on the vehicle, and braking distance was measured by full braking under the condition that ABS was turned on at a speed of 60 km / h on an asphalt road surface having a depth of 1.4 to 1.6 mm. . Evaluation was expressed by the index which makes the braking distance of Example 1 100. The smaller the value, the better.

The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example can achieve both a center wear resistance and a heel & toe wear performance at a high level.

1: Heavy duty pneumatic tire 2: Tread part
3A: Center main home 3B: Middle main home
3C: shoulder main groove 4A: center land portion
4B: Midland part 4C: Shoulder land part
7A: Center horizontal groove 7B: Middle horizontal groove
7C: Shoulder horizontal groove 8A: Center block
8B: Middle Block 8C: Shoulder Block
16A: Center Tie Bar 16B: Middle Tie Bar
16C: Shoulder Tie Bar

Claims (6)

The tread portion includes a center main groove extending continuously over the tire equator in the tire circumferential direction, a pair of middle main grooves extending continuously from both outside of the center main groove in the tire circumferential direction, and both outer sides of the middle main groove. By forming a pair of shoulder main grooves extending continuously in the circumferential direction, the center land portion between the center main groove and the middle main groove, the middle land portion between the middle main groove and the shoulder main groove and the shoulder main groove are formed in the tread portion. Shoulder land between the tread and the ground end,
The center land portion, the middle land portion and the shoulder land portion, as a heavy load pneumatic tire divided into a center block, a middle block and a shoulder block, respectively, by a center cross groove, a middle cross groove and a shoulder cross groove,
The center lateral groove, the middle lateral groove and the shoulder lateral groove are each formed with a center tie bar, a middle tie bar and a shoulder tie bar which raised the bottom of the groove,
The ridge height of the shoulder tie bar is the largest,
When the maximum width of the center land portion is Wcr, the maximum width of the middle land portion is Wmi, and the maximum width of the shoulder land portion is Wsh, the following relationship is satisfied.
0.9≤Wmi / Wcr≤0.98
1.1≤Wsh / Wcr≤1.22 The heavy duty pneumatic tire according to claim 1, wherein the ratio (Wsh / Wmi) is 1.12 to 1.36. The middle point of the tire axial direction of the said center tie bar and the middle tie bar is located in the center area | region of the tire axial direction of the said center cross groove and the said middle cross groove,
The mid-point in the tire axial direction of the shoulder tie bar is located in the outer region of the tire axial direction of the shoulder lateral groove. The heavy-load pneumatic tire according to claim 1 or 2, wherein the maximum raised height of the shoulder tie bar is 70 to 85% of the maximum groove depth of the shoulder main groove. The heavy load air according to claim 1 or 2, wherein the center block, the middle block, and the shoulder block each have a siping extending in the tire axial direction in a central region of the tire circumferential direction of the block. tire. The heavy duty pneumatic tire according to claim 5, wherein a difference between the maximum groove depth of the shoulder tie bar and the maximum depth of the sipping of the shoulder block is 30% or more of the maximum groove depth of the shoulder main groove.

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